1. Field of the Invention
The present invention relates generally to level monitors, and more particularly to a liquid level monitor.
2. Description of Related Art
Liquid level monitors are used in many applications including uses in combination with other components to measure fluid flow variables in open channel flow arrangements. One such level monitor is referred to as a bubble flow meter or bubbler. The bubbler is suitable for various environmental operating conditions since it is unaffected by wind, fluctuation in air or liquid temperatures, turbulence, steam, foam on the surface, corrosive chemicals, debris, oil, floating grease , or lightning.
Known bubblers are instruments that compress air into a reservoir, slowly release that air through an orifice and allow it to flow out the end of an unrestricted tube placed at the bottom of a channel of water. The instrument has a pressure transducer that measures the air pressure after the orifice which pressure is equal to the water head above the end of the tube.
These bubble flow meters are a popular meter, but are not used for certain applications because of some shortcomings. For example, if there is considerable sediment in the channel, the tube may plug. Also, when the fluid head changes dramatically during short intervals of time, some water may enter the bubble tube then exit either when the level drops or when the bubble pressure increases. This wetted tube with an air supply grows algae which can eventually plug the tube. These plugging situations are somewhat alleviated by using a purge valve which is opened at timed intervals to bypass the orifice and release a high pressure stream of air to clear the end of the tube.
Further, since the meter is constantly bringing in air, a desiccant system is required to reduce the relative humidity of the air coming in so as not to damage the mechanics and electronics of the meter. This desiccant has a finite capacity and therefore requires periodic servicing. The compression of air, the need to continuously have air flow to keep water out of the end of the tube even though pressure readings may not be taking place, and the need to periodically purge, all raise the power consumption level to a point where a long term data logging meter using a bubbler is not feasible.
Those concerned with these and other problems recognize the need for an improved liquid level monitor.